1. Field of the Invention
This invention relates to switches used to select the routing of radio frequency transmission lines and, more specifically, relates to an improved actuator for magnetically actuated co-axial switches.
2. Description of the Prior Art
Remotely actuated radio frequency switches having magnetically positioned switchable conductors are described in Canadian Patent No. 2,014,585 entitled "C-, S- and T-switches Operated by Permanent Magnets", naming R. Glenn Thomson, et al. as inventors being issued on Nov 3rd, 1992. With these switches, the function of the actuator magnets is limited to providing the necessary attraction or repulsion impetus to position and secure the transmission line conductor in the selected open circuit or closed circuit position. The actuator magnets are individually located in the actuator to achieve a simple layout whereby a single actuator magnet may service one of the switchable conductors in a particular switch state and a different conductor in another state. In such arrangements, the actuator must be displaced by an amount equal to the separation of the switchable conductors in order to achieve a change of switch state. The magnitude of this displacement partly governs the type and size of motor selected to move the actuator. The actuators of the C-switch, S-switch and T-switch described in the Thomson patent rotate 180.degree., 90.degree. and 120.degree. respectively. Further, where it is desirable for the switch to maintain its selected states in the absence of any holding command or current, either the detent of a permanent magnet motor or some additional detent means must be relied upon to secure the actuator position, thereby increasing the size and type of motor required. The type of switches that are referred to in the Thomson patent as S-switches and C-switches are referred to as C-switches and single-pole double-throw switches respectively in this application. Further switches are described in the Tsoi U.S. Pat. No. 5,063,364 and the Nelson U.S. Pat. No. 4,965,542.
As the transmission lines and switchable conductors of a switch are typically small, the actuator and its motor account for the bulk of the mass and volume of the device. In communication satellite applications, where substantial numbers of such switches are employed on each spacecraft, self-latching and low mass and volume are critical design objectives.